Calcareous Flowers: Tests and Cross-sections of Sea Urchin Spines.
- Photographic study by Richard Howey with some fine photographs of the intricate beauty of these structures.
- http://www.microscopy-uk.org.uk/mag/artaug05/rh-seaurchin.html

Sea Urchins Revisited
- Photographic study by Jean-Marie Cavanihac of the sea urchin with some microscopic features of interest to the amateur naturalist.
- http://www.microscopy-uk.org.uk/mag/artmay02/urchin2.html

Who is in Charge Here?
- Illustrated article by Richard L. Howey considering how creatures with no brains, such as the sea urchin, react appropriately to their surroundings.
- http://www.microscopy-uk.org.uk/mag/artdec02/rhcharge.html

Sea Urchin: A Stinging but Amazing Animal
- Article by Jean-Marie Cavanihac on these animals with many photographs of their development.
- http://www.microscopy-uk.org.uk/mag/artjul00/urchin1.html

Red Sea Urchin
- Information from Wikipedia on this species, Strongylocentrotus franciscanus, including its description, feeding habits, behavior and reproduction.
- http://en.wikipedia.org/wiki/Red_sea_urchin

Photos of Sea Urchins
- Photos of Echinoidea from the Indo-Pacific, with text about behavior, habitat, and characteristics.
- http://www.starfish.ch/collection/seeigel.html

Sea Urchin Embryology
- Laboratory modules using sea urchin eggs to explore fertilization and development.
- http://www.stanford.edu/group/Urchin/

The Echinoids
- Information about sea urchins, such as how they live, feed, and reproduce. There is also an alphabetic listing of their taxa. From The Natural History Museum, London.
- http://www.nhm.ac.uk/palaeontology/echinoids/

Sea Urchin Embryo
- A page from the Laboratory of Embryonic Gene Expression, included here for three beautiful photographs.
- http://www.its.caltech.edu/~mirsky/